prova così...
Codice PHP:
<?php
include("mysql.inc.php");
$myconnect = mysql_connect($db_host, $db_user, $db_password);
$mydb = mysql_select_db($db_name, $myconnect);
$sql = "SELECT DISTINCT articolo FROM gamma ORDER BY articolo ASC";
$st = mysql_query( $sql, $myconnect ) or die(mysql_error());
echo "Regione <select size=\"1\" name=\"articolo\" onchange=\"location.href='pagina.php?articolo='+this.options[this.selectedIndex].value;\">";
while ($data = mysql_fetch_object( $st )){
echo "<option value=\"{$data->articolo}\">{$data->articolo}</option>";
}
echo "</select>";
$articolo = isset($_GET['articolo']) ? $_GET['articolo'] : '';
if($articolo != ''){
$sql = "SELECT variante FROM gamma
WHERE prv_regione = '{$articolo}'
ORDER BY variante ASC
";
$st = mysql_query( $sql ) or die(mysql_error());
echo "Provincia <select size=\"1\" name=\"variante\">";
while ($data = mysql_fetch_object( $st )){
echo "<option value=\"{$data->variante}\">{$data->variante}</option>";
}
echo "</select>";
}